As explained in commonly-owned U.S. Pat. No. 6,899,765, incorporated herein by reference, inspection tools are used in the semiconductor industry for examining semiconductor wafers and photomasks (also known as reticles) at different steps of their respective manufacturing processes. For those less familiar with such matters, during processing the wafers or photomasks are patterned, layer-after-layer, to form a final device. This may involve the deposition, patterning, and/or removal of material on or from semiconductor or other substrates. Because it is important that each of these steps be completed to a high degree of accuracy, the substrates are frequently examined (using inspection tools such as microscopes and the like) during the various processing steps to ensure that they remain as free from defects as is practicable.
The size of defects on or in such substrates tends to be very small; for example, on the order of 50 to 100 nm. While such defects are within the resolution capability of optical inspection tools, those tools must operate quickly and without generating too many false alarms (reported defects which are in fact not defects but random noise created during inspection). In some cases, suspected defects must be further reviewed to confirm their presence or absence, but defect review tools configured for such operations tend to function much more slowly than the optical inspection tools. Moreover, these defect review tools (such as scanning electron microscopes (SEMs) and the like) may need to operate under different conditions than the optical inspection tools (e.g., under an ultra clean, deep vacuum on the order of 10−6 torr), and so having to switch operating environments for the different inspection/defect review operations tends to further reduce overall throughput for a substrate inspection system.
What is needed then is a system that permits more rapid inspection and defect review of substrates and which is capable of accommodating the different operating environments demanded by such inspection and defect review equipment.